Generation of sheared poloidal flows via Reynolds stress and transport barrier physics

A view of the latest experimental results and progress in the understanding of the role of poloidal flows driven by fluctuations via Reynolds stress i s given. Reynolds stress shows a radial gradient close to the velocity shea r layer location in tokamaks and stellarators, indicating that this mechani sm may drive significant poloidal flows in the plasma boundary. Observation of the generation of E x B sheared flows via Reynolds stress at the ion Be rnstein resonance layer has been noticed in toroidal magnetized plasmas. Th e experimental evidence of sheared E x B flows linked to the location of ra tional surfaces in stellarator plasmas might be interpreted in terms of Rey nolds stress sheared driven flows. These results show that E x B sheared fl ows driven by fluctuations can play an important role in the generation of transport barriers.